Analysis of a poly(ε-decalactone)/silver nanowire composite as an electrically conducting neural interface biomaterial

Abstract

Background Advancement in polymer technologies, facilitated predominantly through chemical engineering approaches or through the identification and utilization of novel renewable resources, has been a steady focus of biomaterials research for the past 50 years. Aliphatic polyesters have been exploited in numerous biomedical applications including the formulation of soft-tissue sutures, bone fixation devices, cardiovascular stents etc. Biomimetic ‘soft’ polymer formulations are of interest in the design of biological interfaces and specifically, in the development of implantable neuroelectrode systems intended to interface with neural tissues. Critically, soft polymer formulations have been shown to address the challenges associated with the disregulation of mechanotransductive processes and micro-motion induced inflammation at the electrode/tissue interface. In this study, a polyester-based poly(ε-decalactone)/silver nanowire (EDL:Ag) composite was investigated as a novel electrically active biomaterial with neural applications. Neural interfaces were formulated through spin coating of a polymer/nanowire formulation onto the surface of a Pt electrode to form a biocompatible EDL matrix supported by a percolated network of silver nanowires. As-formed EDL:Ag composites were characterized by means of infrared spectroscopy, scanning electron microscopy and electrochemical methods, with their cytocompatibility assessed using primary cultures of a mixed neural population obtained from the ventral mesencephalon of Sprague-Dawley rat embryos. Results Electrochemical characterization of various EDL:Ag composites indicated EDL:Ag 10:1 as the most favourable formulation, exhibiting high charge storage capacity (8.7 ± 1.0 mC/cm 2 ), charge injection capacity (84.3 ± 1.4 μC/cm 2 ) and low impedance at 1 kHz (194 ± 28 Ω), outperforming both pristine EDL and bare Pt electrodes. The in vitro biological evaluation showed that EDL:Ag supported significant neuron viability in culture and to promote neurite outgrowth, which had the average length of 2300 ± 6 μm following 14 days in culture, 60% longer than pristine EDL and 120% longer than bare Pt control substrates. Conclusions EDL:Ag nanocomposites are shown to serve as robust neural interface materials, possessing favourable electrochemical characteristics together with high neural cytocompatibility.

The Impact of Mandate Contract and Self-Employment on Workers’ Health—Evidence from Poland

“…In Poland, the term self-employment typically refers to individuals, but the legal status of self-employed workers may differ depending on the country. Self-employment is not a homogeneous category; it is a complex and ambiguous phenomenon that presents problems in defining it [ 66 ]. Boegenhold [ 67 ] pointed out that the majority of studies try to relate to the enigmatic typical self-employment, which does not exist in practice.…”

Electrical percolation in extrinsically conducting, poly(ε-decalactone) composite neural interface materials

“…The similar observation was made for conducting polymers, particularly PEDOT, which were found to increase the action potentials of PC12 cells as a response to external electrical stimulation 15 , as well as to stimulate retinal neurons at low voltage amplitudes and low charge densities 16 . In our previous study 13 , we described neural cell stimulation experiments confirming that AgNW are able to transfer charges suitable for cellular depolarization, increasing stimulation efficiency when compared with a control electrode. To determine the minimum amount of a filler required to provide a favourable conductive profile to the polyester matrix, electrochemical impedance spectra (EIS) and cyclic voltammograms (CV) of EDL-based composites were recorded, and the corresponding values of film resistance, capacitance (C) and charge storage capacity (CSC) were extracted.…”

“…To meet these requirements, we described a group of composite materials consisting of poly(ε-decalactone) (EDL) as a soft and biocompatible polymer matrix, and electrically conducting fillers, namely multi-walled carbon nanotubes (CNT), silver nanowires (AgNW) and poly(hydroxymethyl 3,4-ethylenedioxythiophene) microspheres (MSP). EDL, a polymer derived from a commercially available, renewable ε-decalactone, has been recently described as an effective neural interface material, possessing favourable mechanical properties and enhancing neurite outgrowth in vitro 13 . Due to its viscous nature, EDL can be easily used in simple coating processes, such as dip- and spin-coating.…”

“…Poly(ε-decalactone) (EDL) was synthesized according to a method described previously 13 . In short, after purging ε-decalactone (> 99%, Sigma Aldrich) with nitrogen, it was mixed with the catalyst (Ph 3 Bi, Gelest) at 100:1 monomer/catalyst molar ratio and stirred for 7 days.…”

“…In our studies, an aliphatic polyester was chosen as a biocompatible matrix. Poly(ε-decalactone) (EDL), is a soft elastomeric material possessing high biocompatibility, desirable mechanical properties, and is derived from an environmentally sustainable synthesis process 13 . To endow the polymer with electrical conducting properties, the polymer matrix was loaded with selected fillers differing in size and shape, namely carbon nanotubes (CNT), silver nanowires (AgNW) and conducting polymer microspheres (MSP).…”